European Patent Application No. 41 090, in the name of the instant inventor, discloses a composite safety glass which includes, in addition to the above, a polyester sheet between superposed glass and polycarbonate plates.
In the glass structure described in this European application, the polyester sheet is glued to the polycarbonate plates by means of an acrylic resin and is glued to the glass plates by means of a sheet of polyvinyl butyral (PVB).
Numerous tests have been ascertained that attachment of the polyester sheet by means of PVB is not satisfactory because it is very difficult to make PVB adhere perfectly to a sheet of polyester.
Moreover, it has also been noted that, disadvantageously, during calendering of the superposed layer or "sandwich" assembly to make the PVB adhere to both the glass and polycarbonate plates, the polycarbonate plate has a tendency to deform.